Understanding Load Charts
The safe and proper operation of cranes and excavators used for lifting is primarily the operator’s responsibility. Therefore, both managers and operators need to understand crane and excavator load charts. Foremen and other managers should understand and utilize the charts so that they can plan the lift and ensure that loads are positioned where the equipment can safely lift the load and move it to where it needs to be placed. For example, if a truckload of pipe is positioned too far away from the crane or equipment, it may not be safe to lift the pipe off the truck and place it next to or in the trench.
The OSHA Crane Standard – Subpart N requires crane operators to be certified by Nov. 10, 2017. In order to pass the test, operators will have to demonstrate their ability to use load charts, which are appropriate for each type of crane that they will be certified to operate.
Although excavator and backhoes are exempt from the new rule, they will continue to be frequently used by underground utility contractors to lift pipe and materials. Operators will not have to be certified, but they still need to know how to use the appropriate load charts to ensure safe handling of loads.
This article is intended to provide operators and managers with a basic understanding of how to read and understand load charts. Before operating cranes or equipment, all operators must be fully trained in how to read and use the load charts and to safely operate the machine. NOTE: This article is NOT intended to provide the necessary training required for operators or anybody responsible for lifting and rigging. Job specific training is required to ensure that operators are qualified to operate machinery.
How to Use Load Charts
Only load charts that are found in the equipment operation manual or posted by the manufacturer in the equipment should be used. The load charts are specific to the make, model and configuration of a specific piece of equipment. Don’t forget to include adjustments for buckets, boom extensions, load blocks, hoisting rope and other attachments that will alter the lifting capacity of the crane or equipment used to perform the lift. For example, the weights of hooks, blocks, buckets, slings and other handling devices must be added to the load or deducted from the equipment lift capacity.
Crane Load Charts
Crane load charts are different than excavator and backhoe load charts. Although the basic concepts are the same, there are differences. For example, the closer a crane is to the load and the higher the boom angle, the greater the lifting capacity. This rule does not always apply to excavators. Before a lift can be made safely, the operator must know the weight of the load and how far the load is from the center of the boom turntable which is referred to as the load radius. One thing to remember is that if you are measuring from the front of the crane as is often done, be sure to add the distance to the center of the boom turntable. If the load will be lifted from a point above ground level, you will also need to know from what height it will be lifted to ensure that the boom can be placed high enough above the load and still ensure a safe lift. You should never lift a load if the cable is at an angle.
By referring to the load chart, a crane operator can determine what angle the boom will have to be to ensure that he or she is directly above the load. Before lifting a load with a crane, the operator must check the boom angle indicator, which will provide the angle of the boom from horizontal.
Reading the Load Charts
In this example, the load of concrete pipe is on the truck waiting to be set next to the trench. We are using a small Broderson truck-mounted telescopic boom crane, which is set without extending the outriggers behind the flatbed truck carrying the pipe. Each 8-ft section of 36-in. pipe weighs 5,240 lbs. If the pipe is 16 ft from the front of the flat bed truck, will it be safe to lift the pipe and swing it 90 degrees and set it down 26 ft away from the side of the crane?
First determine the boom angle by referring to the chart. Remember to add the distance from the front of the truck to the center of the boom turntable (approximately 10 ft). Therefore, when referring to the chart use a radius of 10 ft+16 ft=26 ft. Although this arrangement will permit us to use different boom angles, we will use 45 degrees for this lift.
The next step is to check the capacity chart (above) to see if the crane is capable of safely lifting the 5,240-lb pipe. The chart shows it is safe to lift 6,000 lbs (blue) at a radius of 26 ft over the front of crane with the crane resting on rubber tires. However, when looking at what the crane can safely lift off the sides or rear, the chart indicates the crane can only handle 3,300 lbs on rubber (yellow) and 4,900 lbs with outriggers in and down (red). Therefore, the only way this crane can be used to handle this load as planned is with the outriggers down and fully extended — 11,900 lbs (green).
The crane manufacturer also provides a set of lifting notes that should be reviewed before any lift.
The notes include, but are not limited to, tire pressure for using the crane on rubber or for pick-and-carry operations, outriggers being placed on a firm level surface and not operating at a radius where no capacity is listed on the chart. If the desired load radius falls between two load radii on the chart, it is recommended to use the load radius with the lower capacity and not to try to interpolate between the numbers. Always follow the manufacturer’s recommendations.
When Excavators and Backhoes Are Used for Lifting
Lifting capacity charts for excavators and backhoes are similar, but differ from crane load charts.
As with the crane, it is important to know the lift radius, which is the distance between the center of the machine’s swing bearing and the center of the load hook. You will also need to know the height at which the lift will begin and end, which could be above or below ground level.
The lift capacity of excavators and backhoes changes radically as the position of the load changes. Therefore, planning ahead is important for a safe lift. Is the machine capable of handling the load safely? Prior to starting a lift, the operator should know the weight of the load and look at the machine’s load chart, which should be mounted in the cab and be legible from the control position.
Excavator and backhoe load charts provide lift capacities for a range of lift heights and radii. The chart will also show the capacity over both ends and sides of the machine. Similar to cranes be sure to use the chart that matches the specific machine and configuration. When lifting with the bucket in place, most manufacturers require the operator to subtract the weight of the bucket from the lift capacity because the weight of buckets vary considerable based on size. Follow the manufacturer’s recommendations for attaching the load and never use the teeth of the bucket or an attachment that has been welded to the bucket unless it has been designed and certified by an engineer.
For example, using the same pipe — 5,240 lbs — that we set on the ground with the crane in the previous example, determine if the Volvo EC240C L hydraulic excavator can lift the pipe from 15 ft away from the side of the trench and place it 10 ft below ground, 20 ft in front of the excavator measured from the swing bearing.
Using the starting point for the lift, which is ground level (0 ft) move across to the column that applies to lifting the load from 15 ft to the side of the equipment and you will see that this machine can easily handle the initial lift — load capacity 19,840 lbs (yellow). Then check the capacity for where the load will be placed, which is 10 ft below ground and 20 ft in front. With a capacity of 20,480 lbs (green), the machine can handle the load. Note how the load capacity drops to 13,260 lbs (red) as the load is moved further away from the excavator as the pipe is placed in the trench.
Planning ahead and knowing that the equipment you intend to use has a capacity to lift the pipe, trench boxes and materials that will have to be moved ensures a safer, more efficient job. It will also reduce the possibility of damaging the equipment due to overloading and/or tipping over.
For more information about rigging and lifting, visit the NUCA store at www.nuca.com.
George Kennedy is NUCA’s vice president of safety. Tags: George Kennedy, NUCA, Safety